<?php
//比较运算符
$a = [true, false, '9', '123a'];
foreach ($a as $row) {
    foreach ($a as $col) {
        $b = $row == $col; //2.5.6.2 松散比较 ==
        if ($b) echo "1\t";
        else echo "0\t";
    }
    echo "\n";
}
//is_numeric
$a = ['12', '+12', '-12', '012', '0x1a', '2e5', '2aaa'];
foreach ($a as $value) {
    echo is_numeric($value) ? "true" : "false", "\t";
}
echo "\n";

//2.5.6.3 严格比较 ===
var_dump(123 === '123');